The present invention relates to novel adhesives and, more particularly, to novel adhesives which can be coated onto an aluminum backing material to provide so-called foil tapes which meet the very severe Underwriter Laboratories, Inc. (UL) 181A requirements and specifications for use with rigid fiberglass air ducts.
Foil tapes, e.g. pressure-sensitive or heat-bonded aluminum tapes are of course known in the art. It is also heretofore known to employ foil tapes for such purposes as closure systems for use with factory-made air ducts and connectors. However, recently UL has imposed very severe standards for this usage. Consequently, the primary task of this invention can be said to develop a novel aluminum (foil) tape which will meet the recent UL requirements and specifications, as detailed hereinafter, for the aforementioned usage.
______________________________________ U.L. SPECIFICATIONS ______________________________________ Test No. Description ______________________________________ Peel Adhesion Three samples from each of three separate rolls of tape cut in 1 inch (25.4 mm) wide by 12 inches (305 mm) long strips are to be tested. The tape samples are to be applied (as specified in ASTM D-3330-83) to a stainless steel panel with a mechanically operated roller weighing 10 pounds (4.53 kg.). The roller is to pass over each sample five times in each direction. The test load is to be applied 15 minutes after completion of the rolling. 1 The average peel adhesion strength of each roll of aluminum tape shall be .gtoreq. 3.75 lbs. (60 oz) per inch of width 4 (0.66 N/mm) of tape, with no individual sample having a value .ltoreq. 3.20 lbs (51.2 oz) per inch of width (0.56 N/mm). Shear Adhesion The shear adhesion strength of aluminum tape is to be determined in accordance with ASTM D-3654-82, as modified in the following description. One sample from each of four separate rolls are to be tested. Samples are to be cut in 1-inch (25.4 mm) wide by 6-inch (152 mm) long strips. The cut samples and specified stainless steel panels are to be maintained at the specified application conditions a minimum of one hour prior to applying samples to the panels. The tape is to be applied to the panel with a mechanically operated roller weighing 10 pounds-mass (4.53 kg). The roller is to pass each sample five times in each direction. Using a cutting gig or razor blade, the rolled portion of the sample is to be trimmed to a 1 inch by 1 inch square on the panel, such that the remaining test sample measures 1 inch by 5 inches. The tape is to be allowed to dwell on the panel for the specified time. After dwelling, the clamp is to be placed on the free end of the sample, insuring that the clamp extends completely across the width of the specimen and is aligned to uniformly distribute the load. The specified test load is then to be applied to the clamp gently so as not to cause any shear impact force on the sample. The load is to be applied for the specified test duration. The test panel is to be positioned at 2 degrees from the vertical so that the test substrate forms a 178.degree. angle with the extended tape sample. Individual samples of the tape are to be tested in accordance with each of the conditions as set forth hereinbelow: ______________________________________ Application Dwell Test Test Condition Time Condition Load Duration ______________________________________ 2. 40.degree. F. 15 minutes 40.degree. F. 5 lbs. 6 hours (4.4.degree. C.) (22.2 N) dry substrate 3. 73.4.degree. F. 15 minutes 73.4.degree. F. 5 lbs. 6 hours (23.degree. C.) 50% RH 4. 73.4.degree. F. 24 hours 73.4.degree. F. 10 lbs. 120 hours (23.degree. C.) 50% RH 5. 73.4.degree. F. 15 minutes 150.degree. F. 5 lbs. 6 hours (23.degree. C.) (65.6.degree. C.) 50% RH ______________________________________
The shear adhesion strength of the tape (in each of the above tests) shall be such that the tape is able to maintain the test loads specified in the tests for the indicated test durations without evidence of separation or slippage in excess of 1/32 inch (0.79 mm).
The aforementioned tests (peel adhesion and shear adhesion) constitute the essential criteria which are critical to achieve in order to provide an aluminum tape meeting UL specifications for use with air ducts and connectors. However, for the sake of accuracy, it is to be noted that they are not the only tests which must be passed to satisfy UL specifications. One such test is a tensile strength test for the tape backing (foil). Another is peel adhesion at 20.degree. angle. The former is not relevant to this invention and the latter will be met if the adhesive passes the five critical tests enumerated above.
Other UL criteria, specifically surface burning characteristics, mold growth and humidity tests, temperature/pressure cycling tests, burning test and manufacturing and production tests, as detailed in UL181A, are not difficult to meet and for purposes of a clear understanding of the nature and objects of this invention need not be described.
My aforementioned copending application, Ser. No. 019,832 (PF1040) is also directed to the task of providing an adhesive which can be employed for preparing metal foil adhesive tapes meeting UL specifications. In this copending application, the task is solved by providing an adhesive composition comprising a crosslinked copolymer of:
(1) at least one macromolecular monomer;
(2) at least one ethylenically unsaturated carboxylic acid containing 3-5 carbon atoms;
(3) at least one acrylic or methacrylic acid ester of a non-tertiary alcohol having 1-14 carbon atoms; and
(4) at least one vinyl ester of a saturated carboxylic acid;
the tetrapolymer being crosslinked with a crosslinking agent reactive with said carboxylic acid moiety through its reactive hydrogen atom, the macromolecular monomer being a compound of the formula: EQU R--Z--X
wherein R is lower alkyl, Z is a repeating monomeric unit selected from the group consisting of styrene, alpha(methylstyrene), isoprene, butadiene and mixtures thereof; n is a positive integer such that molecular weight is in the range from about 5,000 to about 50,000 and x is a polymerizable end group selected from the group consisting of: ##STR1## where n' is a positive integer from 1-4 and R' is alkyl having 1-4 carbon atoms.
The only commercially available macromolecular monomer of this description and hence of necessity the preferred one is 2-polystyrylethyl methacrylate which has been sold by Sartomer Company, a subsidiary of Atlantic Richfield under the name Chemlink .RTM. 4500 Macromer .TM. Monomer.
However, subsequent to the invention described and claimed in the aforementioned copending application, Applicant and his assignee, The Kendall Company, was advised that the Chemlink .RTM. Macromer would no longer be commercially available to them.
The task of the present invention can accordingly be described as being to prepare a metal foil tape meeting UL requirements which is not necessarily better than the invention in the earlier copending application, but which utilized readily obtainable starting materials.